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How much domestication? About 5000 species have been grown for human food – less than 1% of all plant species thought to exist Today about 150 species are commercially grown for food (not including spices) About 50 very productive species supply almost all of our caloric needs

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Benefits of Domestication 10,000 years ago, before agriculture began, the world’s total human population was about 5 million. There was one person for every 25 square kilometers. Today we have more than 7 billion people, with a density of just over 25 people per square kilometer

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As agriculture developed humans selected for: 1. Plants that provide enough calories to meet our basic energy needs. This usually comes from cereal grain or root carbohydrates. 2. We also selected for a balanced nutritional intake - this tends to develop in any system where the cultivator eats and depends upon on what he/she grows.

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Plants from Peru Potato -Solanum tuberosum and many related species Quinoa - Chenopodium quinoa Amaranth – Amaranthus (3 species) tomatoes and peanuts may have really originated in Peru and then been taken to Mexico

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Potato

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Quinoa

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First ethnobotanical rule of food production In indigenous agriculture where the crops are consumed and not sold, there evolves and is maintained a reasonable level of nutritional adequacy

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Second ethnobotanical rule of food production In indigenous agriculture where the crops are grown mainly or only for sale, there develops an expanding surplus of food. The overall objective of such agricultural systems is to replace a pre-existing (natural) plant community with a cultivator-made community

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It then follows that: If the potentially unstable increase in food production and human population is to be maintained, it must be consistent with three aims: 1. To operate at a maximum profit (labor/yield). 2. To minimize year-to-year instability in production. 3. To operate so as to prevent long-term degradation of the production capacity of the agricultural system.

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Mexican Corn Growing

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Mexican Corn Varieties

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Darwin on Artificial Selection “Although man did not cause variability and cannot even prevent it, he can select, preserve, and accumulate the variations given to him by the hand of nature almost in any way which he chooses; and thus can certainly produce a great result… Selection by man may be followed either methodically and intentionally, or unconsciously and unintentionally… We can further understand how it is that domestic races of plants often exhibit an abnormal character, as compared to natural species, for they have been modified not for their own benefit, but for that of man.”

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Western Yarrow

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Street in Cuzco, Peru with advertisement for California seeds

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Plant Germ Plasm The first category of germ plasm includes the native or indigenous varieties of cultivated crop plants used elsewhere in commercial agricultural production. At present many of the major crop plants have a limited genetic base, as these have been developed through a series of selections that emphasize yield often at the expense of insect or disease resistance, environmental tolerance, multiple use, etc.

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Seed Savers, Decorah, Iowa

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Stowe, England – Apple Festival

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Spread of Southern Corn Leaf Blight

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Southern Corn Leaf Blight

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Close up of Southern Corn Leaf Blight

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Southern Corn Leaf Blight – damage to ear

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Sweet Potato

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Healthy Sweet Potatoes – Ipomoea batatas

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Sweet potatoes with black rot

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Sweet potatoes with soft rot

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Sweet potatoes with russet crack

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Sweet potato attacked by nematodes

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Sweet potato with stem rot Healthy sweet potato

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Plant Germ Plasm The second category of germ plasm material includes the identification and collection of wild relatives of the more commonly cultivated plants.

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Wild Tomato Species From Peru Domestic High Altitude Another S. sisymbrifolium

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Plant Germ Plasm The third category includes plants not yet in the economic system and not related to domesticated plants. These may have properties of great value to us, but these can be very difficult to identify.